Abstract: Polydiene rubbers are commonly compounded with carbon black in making a wide variety of rubber articles including tires, hoses and belts. It is generally desirable for the carbon black to be well dispersed throughout the polydiene in order to attain optimal physical properties. For instance, the traction and rolling resistance of tires which are made utilizing such rubbers can be improved by better dispersing the carbon black throughout the polydiene. The subject invention discloses a technique for capping polydienes in order to improve their affinity for carbon black. The present invention more specifially reveals a process for preparing a polydiene having a high level of affinity for carbon black which comprises reacting a metal terminated polydiene with a capping agent selected from the group consisting of (a) halogenated nitriles having the structural formula X--A--C.tbd.

Abstract: Metals from Groups I and II and organometallic compounds thereof can be used to catalyze the polymerization of diene monomers into polymers. The polymers formed in such polymerizations are terminated with the metal used to catalyze the polymerization and are sometimes referred to as living polymers. Very useful blends of such polymers can be made by utilizing the process of the present invention.